The present invention relates to a storage system for storing data of computers (or servers), and particularly to a storage system including a plurality of storage devices which are constituted by a tiered structure, and each of the storage devices is constituted by a plurality of disk devices. It also relates to a method for a data transfer between the tiered storage devices in the storage system connected with a NAS (Network Attached Storage) for input/output of files, and allocation of volumes provided by the tiered storage devices to directories provided by the NAS.
In these years, the improvement of computational performance has been achieved remarkable breakthrough by a HPC (High Performance Computing) purpose computer or a supercomputer. In a few years, it is predicted that a supercomputer will appear with a computational performance of a Peta FLOPS (Floating Operation Per Second) class, and will also appear with a still better computational performance of an Exa FLOPS class, about ten years after. With this improvement, it is also predicted that a magnitude of calculation for such as scientific calculations performed by using the supercomputer will become large, and individual file sizes to be inputted and outputted to/from the supercomputer will also become large from GB (Giga Byte) to TB (Tera Byte) order. Therefore, it is predicted that a storage system to be connected with the supercomputer will require a capacity ranging from PB (Peta Byte) to EB (Exa Byte) class. Further, it is assumed that an I/O processing performance for the storage device will require to be improved to the extent of 1 to 2 orders from the present performance because of a necessity for performing the input/output of the TB class files in high speed.
Conventionally, in the case of a storage system used for the supercomputer, midrange-class storage devices having a good cost performance are provided in correspondence with the number of nodes in the supercomputer and operated in parallel to obtain an I/O processing performance of the storage devices suitable for the I/O processing performance requested by servers or computers.
Further, performance requirements are various to be requested for the storage devices used for the supercomputer, that is, a high sequential performance is demanded to input/output large-sized files in high speed, and a high transaction performance is also demanded to input/output a number of files simultaneously.
For a purpose of responding to the performance requirements described above, JP-A-2004-70403 has disclosed a technique such that volumes storing files are distributed in response to a performance requested from computers or applications. According to a method in the document, file storing requirements for every business application (requirements of a performance, reliability, etc. to be requested for volumes for storing files) are determined in advance. Further, the side of storage devices provides a table having a specification of the performance etc. itself for a file-storing volume in advance. The foregoing table is then referred to every file in every storing requirement of the application to distribute storing destination volumes.